Hi hackers, It's been a while since the last time I explored how PostgreSQL stores the data on disk, so I decided to refresh my memory. All in all this topic is well documented, but there is one question that I couldn't find an answer to quickly.
>From README.HOT: > If an update changes any indexed column, or there is not room on the > same page for the new tuple, then the HOT chain ends: the last member > has a regular t_ctid link to the next version and is not marked > HEAP_HOT_UPDATED. So t_ctid will point to the newer version of the tuple regardless of whether HOT is used or not. But I couldn't find an answer to how t_ctid is used when a tuple is not a part of a HOT chain, or is the last item in the chain. Which brings a question, maybe it shouldn't take that much space on disk. Probably I missed something. Could you please point me to the document or comments that describe this topic? Or maybe we should add a brief comment to HeapTupleHeaderData.t_ctid field and/or README.HOT that would clarify this. For sure this could be learned from the code, but I believe clarifying this moment in the comments could simplify the life of the newcomers a bit. -- Best regards, Aleksander Alekseev
